// Assume minuend >= subtrahend >= 0
void Sub(int minu[], int subt[], int diff[], int max_digits) {
   int update[max_digits];
   update = minu;  // Array assignment
   for (int bit = 0; bit < max_bits; bit++) {
      if (update[bit] < subt[bit]) {
         update[bit] += 2;
         int i = bit + 1;
         while (update[i] == 0) {
            update[i] = 1;
            i++; 
         }
         update[i] = 0;
      }
      diff[bit] = update[bit] - subt[bit];
   }
}
